How do you overcome back ache when cycling?

That is probably because your seat and more frame size needs to be adjusted. Generally when i go riding i get a little ache because my seat is up high so i can extend my legs to their full length so i can get as much power out of them as possible. Ive never found a solution however, that solves the problem without creating another. If you lower your seat your back pain will be less of a problem but its not healthy for your knees to be bent all the time.